Display devices such as liquid crystal display devices have been applied in a wide range of fields from large-sized display devices such as TV sets to small-sized display devices such as mobile phones, and those with higher added value have been developed. In recent years, in view of improvement in convenience of mobile devices for example, development of display devices with low power consumption has attracted attention.
For example, Patent Document 1 discloses a technique for reducing the power consumption of a liquid crystal display device, in which all signal lines are electrically disconnected from a signal line driver circuit and a high impedance state is formed in order to keep the voltage of each signal line constant in a break period during which no scan line and no signal line are selected.
Non-Patent Document 1 discloses a structure for reducing the power consumption of a liquid crystal display device, in which the refresh rate in moving image display is made to be different from that in still image display. Further in Non-Patent Document 1, in order to prevent perception of a flicker due to fluctuation of a voltage applied to a liquid crystal element which is caused by switching of a signal between a break period and a scanning period in the case of displaying a still image, a technique for preventing the fluctuation of a voltage applied to a liquid crystal element, in which AC signals with the same phase are applied to a signal line and a common electrode also in the break period, is disclosed.